(a) Field of the Invention
The present invention relates to a switching mode power supply (SMPS) and a driving method thereof.
(b) Description of the Related Art
A switching mode power supply (SMPS) is a device that rectifies an input AC-link voltage to an input DC-link voltage and converts the input DC-link voltage to a DC-link output voltage of a different level. In this case, the DC output voltage is greater or less than the input DC voltage. Such an SMPS is used in most battery powered electronic devices, and particularly in mobile phones and laptop computers.
Switching noise generated during a switching operation of the SMPS causes electromagnetic interference (EMI) between electronic devices that include the SMPS and receive power therefrom. The switching noise includes noise components generated by harmonic components of a switching operation frequency of a switch of the SMPS. When the EMI is generated, operations of peripheral electronic devices are disturbed. In order to prevent generation of the EMI, an external device such as a filter is additionally provided to the SMPS for blocking the EMI. Accordingly, production cost is increased.
Another method to block the EMI is to change a switching operation frequency of a switch that controls operation of the SMPS. Hereinafter, the switch will be referred to as a power switch. For a control circuit of a conventional SMPS, a passive element or a digital circuit is used for changing the switching operation frequency. Furthermore, the passive element or the digital circuit is formed inside the control circuit of the SMPS so that a user of the SMPS cannot control a degree of frequency change.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.